Stacked solar distiller using water to storage heat for high-temperature evaporation

Abstract

Solar stills can produce freshwater with low or even no carbonization to alleviate the problem of freshwater resource scarcity. However solar distiller's operation period is limited by the intermittence of solar energy, and the Gained-output ratio (GOR) is determined by operation temperature. To further develop efficient solar distillers, this paper investigates a stacked solar distiller with high evaporation temperature, utilizing water to storage heat. A mathematical model of a triple-stacked solar distiller (TSD) was established to describe the internal heat and mass transfer processes. Then an experimental device was built. The experiments under steady-heating and outdoor solar-heating have been conducted. The steady-heating testing results show that, when the evaporation temperature of TSD reaches 79.9 °C, the GOR reaches 2.00. The theoretical model can accurately predict the operating parameters of the distiller, with the deviation of the theoretical temperature from the experimental value within 0.9 °C and the GOR deviation ranging from 2.2 % to 21.0 %, under steady-heating testing. The outdoor testing results show that, at an average daily irradiance of 606 W/m2, the maximum evaporation temperature is above 90.0 °C, achieving a water yield rate of 2.53 kg/(h·m2) and the maximum instant GOR of system closing to 2.23. Combined with nighttime water yield attributing to heating storage, a water yield of 28.00 kg/(d·m2) can be achieved. This research may provide a good scheme for the scenario of small-scale distributed solar desalination demands.